Oobu (or Ubu, or Ubb-Ubb) was the octopus who befriended and rescued Tarvu when he landed in the ocean from the Heavens.

Oobu appears as a vision to a group of shepherds. He often appeared like this to random people throughout the world.

Oobu and his wife Ootati, their children Oppo and Ippi along with Oobu's father Oopapa, kept Tarvu alive by feeding him ink and shrimps. They lived together in the seas for nine years, and Tarvu became a very good swimmer. Oopapa sadly died along the way, being eaten by a giant wooly sea-tortoise, called Karkippenah. This species (known as 'Tortimikeppi') is now extinct. Tarvuists believe that this was Tarvu's revenge for the death of his adopted aquamarine grandfather. However, some zoologists have reported sightings of tortimikeppi in lakes in Hungary, Romania and Sri Lanka, although they have never been photographed.

Tarvu never forgot his adopted octopus family, and forbad the eating of calamari.